1. Field of the Invention
The present application has for an object novel cationic 4,5-diaminopyrazoles, a process for producing them and colorants containing these compounds.
2. Description of Related Art
Oxidation dyes have attained substantial cosmetic significance in the field of conventional hair dyeing. The color is created by reaction of certain developers and couplers in the presence of an oxidant. Besides the creation of color effects, very high requirements are placed on oxidation dyes that are intended for the treatment of human hair. On the one hand, the dyes must be harmless from a toxicological and dermatological point of view and they must not be sensitizing. Moreover, it must be possible, by a combination of suitable developers and couplers, to produce a wide range of different color nuances. Furthermore, the hair colorations produced are required to have good wash fastness, light fastness, perspiration resistance, resistance to permanent wave treatments, acid resistance, base resistance and abrasion resistance. At any rate, such hair colorations must remain stable for at least four to six week under normal everyday conditions.
In the past, 4-aminophenol has been the primary developer used to cover the important red range. Because of concerns about the physiological compatibility of this substance, derivatives of pyridine and pyrimidine have also been used, but they were not satisfactory from a coloring standpoint. 4,5-Diaminopyrazoles and 4,5-diaminopyrazoles substituted in the 3-position have also been used in place of 4-aminophenol. Moreover, it is known from WO 00/43367 to use cationic pyrazole derivatives of a broad general formula in hair colorants. Most of the compounds referred to in WO 00/43367, however, cannot be prepared by processes presented therein and thus are not available.
Whereas most oxidation dyes show hardly any weaknesses on undamaged hair, they can cause pronounced differences on damaged hair. The hairdresser thus knows from everyday practice that dyes are not uniformly taken up by the hair to be dyed. Whereas, as a rule, the hair roots are intact, with the passage of time the hair tips show damage due to weathering effects, frequent washing and combing, damage that gradually increases from the hair roots to the hair tips. Hence, when such hair is dyed, nonuniform coloring can result because of the nonuniform condition of the hair between the roots and the tips. Another problem lies in the fact that when dyed hair is washed, the dyes are more strongly washed out from the more strongly damaged parts of the hair than from undamaged parts, depending on the degree of hair damage, which after a few washings can gradually become more evident.
To cover the red range in particular, the need continued to exist for suitable dyes capable of being taken up readily and uniformly and of giving colorations with improved stability against shampooing on a wide range of hair qualities, particularly on hair damaged by permanent waving or bleaching.
We have now found that certain cationic pyrazoles meet the afore-said objective in outstanding fashion.